Print labels directly to Brother QL label printer using brother_ql lib.

print_label.py

from PIL import Image, ImageDraw, ImageFont
from brother_ql.devicedependent import label_type_specs
from brother_ql import BrotherQLRaster, create_label
from brother_ql.backends.helpers import send


PRINTER = {
    'model': 'QL-800',
    'address': 'usb://0x04f9:0x209b'
}


def get_font(text, size, margin, fontname, draw, start=100):
    ' Return font after calculating largest size which fits in box of given size.'
    fontsize = start
    while True:
        font = ImageFont.truetype(fontname, fontsize)
        txtsize = draw.multiline_textsize(text, font=font)
        if txtsize[0] >= size[0] - (margin * 2) or txtsize[1] >= size[1] - (margin * 2):
            # reduce font size and try again
            fontsize -= 2
        else:
            # print(f'Using fontsize {fontsize}')
            return font


def draw_address_label(body, memo, size):
    img = Image.new('L', size, 'white')
    draw = ImageDraw.Draw(img)

    margin = 0
    font = get_font(body, size, margin, 'times.ttf', draw, 60)

    # Center text horizontally and vertically in image.
    # Set anchor point to the middle (half width and half height of image size)
    # and anchor alignment to middle/middle (mm) of text.
    draw.multiline_text((size[0]/2, size[1]/2), body, fill='black', font=font, anchor='mm', align='center')

    smallfont = ImageFont.truetype('times.ttf', 20)
    # And memo to bottom left corner
    draw.text((margin, size[1] - margin), memo, fill='black', font=smallfont, anchor='ld', align='left')

    # Outline with rounded rect for debuging
    # draw.rounded_rectangle([(0, 0), (size[0] - 1, size[1] - 1)], radius=10, outline='black', width=1)

    return img


def draw_file_label(body, memo, size):
    img = Image.new('L', size, 'white')
    draw = ImageDraw.Draw(img)

    margin = 0
    font = get_font(body, size, margin, 'times.ttf', draw, 50)

    # Add body to top left
    draw.multiline_text((margin, margin + 50), body, fill='black', font=font, anchor='la', align='left')
    # And memo to top right corner
    draw.text((size[0] - margin, margin), memo, fill='black', font=font, anchor='ra', align='right')

    # Outline with rounded rect  for debuging
    # draw.rounded_rectangle([(0, 0), (size[0] - 1, size[1] - 1)], radius=10, outline='black', width=1)

    return img

def print_label(style, label_type, body, memo=None, cut=True, printer=PRINTER):
    '''
    Print a label directly to printer.

    style: The style (layout) of the label. One of `address` or `file`.
    label_type: The type (size) of label in the printer. Valid values include
                any `name` listed in the output of `brother_ql info labels`.
    body: The main body of the label.
    memo: Optional secondary content printed to the label.
    cut: Instruct the printer to cut after printing the label. Default: `True`.
    printer: A dict specifying the printer `model` and `address` to send the print job to.
    '''

    memo = memo or ''

    # Width and height are switched so we can draw with horizontal text. Image will then be rotated.
    size = (
        label_type_specs[label_type]['dots_printable'][1],
        label_type_specs[label_type]['dots_printable'][0]
    )

    if style == 'address':
        img = draw_address_label(body, memo, size)
    elif style == 'file':
        img = draw_file_label(body, memo, size)
    else:
        raise ValueError(f"'style' must be one of 'address' or 'file'. Got '{style}' instead.")

    qlr = BrotherQLRaster(printer['model'])
    create_label(qlr, img, label_type, cut=cut, rotate=90, dpi_600=False)
    send(qlr.data, printer['address'])


if __name__ == '__main__':
    img1 = draw_address_label('Firstname Somelongname\nSome  Building\n123 Any Street Apt C-3\nAnytown PA, 12345', 'No. A.D. 123 of 2021', (991, 306))
    img1.save('address_label.png')
    img2 = draw_file_label('Somelongname, Firstname\nSomelongname, Othername & Another, Name', '123-2021', (991, 306))
    img2.save('file_label.png')

    # To print one of the above generated images, run the following command:
    # brother_ql -b pyusb -m QL-800 -p usb://0x04f9:0x209b print -l 29x90 address_label.png

    # To print a label directly from Python, do this:
    print_label('address', '29x90', 'Firstname Somelongname\nSome  Building\n123 Any Street Apt C-3\nAnytown PA, 12345', 'No. A.D. 123 of 2021')